1. Field of the Invention
The present invention relates to an image forming apparatus capable of preventing abnormal termination of an active job because of a power outage, and to a method of controlling the apparatus.
2. Description of the Background Art
As one type of image processing apparatuses as electronic equipment, an image forming apparatus (typically a copy machine) for forming an image on a sheet of recording paper has been introduced to many places of business (companies and offices). In such a place of business, it is a common practice to have an image forming apparatus having a printer function or copy function connected to a network and to share the apparatus by a plurality of users. An MFP (MultiFunction Peripheral) as one type of such image forming apparatuses has a plurality of basic operational modes including a copy mode, a facsimile mode (hereinafter facsimile will be also denoted as FAX), a network compatible printer mode and a scanner mode.
Generally, a copy machine consumes much electric power at the time of activation from power on and at the time of executing the copy function. In an image forming apparatus having an image forming unit utilizing electro-photography process, a toner image recorded and reproduced on a photoreceptor is transferred to a sheet of recording paper. A heating and fixing unit includes a heat source such as a heater, and it fixes the toner that has been transferred to the sheet of recording paper on the sheet of recording paper by prescribed heat and pressure. Therefore, in order to provide an environment enabling speedy image formation, it becomes necessary to keep constant the temperature of the heating and fixing unit. For this purpose, power conduction to the heat source such as the heater must always be controlled. By way of example, temperature of the roller in the fixing unit is kept at a certain temperature even in a waiting period (so-called ready state), so as to make shorter the time before copying is executed.
Such control naturally increases power consumption. It is quite wasteful to keep the fixing unit warm as described above at a time of day when frequency of use of the copy machine is low. Since the heater requires much electric power, this poses a significant problem from the viewpoint of energy saving. Recently, reduction of power consumption at the places of business comes to be an important issue, and constant consumption of much electric power as described above is undesirable.
Japanese Patent Laying-Open No. 2005-345894 (hereinafter referred to as '894 Reference) discloses a technique of reducing wasteful power consumption by stopping power conduction to the fixing unit if no operation is made for a prescribed time period after the end of copying.
As a method of saving power if date and time when the copy machine is not used is known in advance, Japanese Patent Laying-Open No. 2005-71269 (hereinafter referred to as '269 Reference) discloses a method of setting an image processing system to a power saving mode on holidays. Japanese Patent Laying-Open No. 2002-55569 (hereinafter referred to as '569 Reference) discloses a technique of saving power by switching an image forming apparatus to the energy saving mode at a peak season when general people consumes much power.
The techniques disclosed in '894, '269 and '569 References, however, cannot always cope with a power outage on short notice due to external factor, independent from the schedules set in the apparatuses. More specifically, it is not always possible to change the schedule before a power outage in consideration of expected time when the power outage starts (hereinafter referred to as outage start time). In such a situation, it may become impossible because of the power outage to normally end or temporarily suspend a print job that is being executed, which is inconvenient. Abnormal termination caused by a power outage may require some trouble-shooting work when the image forming apparatus is restarted after the end of outage. By way of example, if paper jam has occurred, work to eliminate the jam would be necessary. Some types of troubles may be difficult to fix.